1. Field of the Invention
The present invention relates to a laser processing apparatus including a fiber laser light source.
2. Related Background Art
A laser processing apparatus is an apparatus that processes an object to be processed by irradiating the object with laser light. Further, as an example of a laser processing apparatus, an apparatus that comprises a fiber laser light source is known. In a laser processing apparatus comprising a fiber laser light source of this kind, the laser light emitted from the fiber laser light source has a predetermined divergence angle and the laser light is therefore temporarily collimated by a collimator with the beam diameter in an enlarged state. The laser light having been collimated in this manner is condensed on the object by the condenser lens (laser light irradiation).
In addition, an optical isolator is disposed on the light path between the collimator and condenser lens. The optical isolator is provided in order to prevent reflected light (return light) that is produced as a result of the laser light irradiation with respect to the object from returning to the fiber laser light source. As a result, protection of the fiber laser light source is sought. In a laser processing apparatus, because the laser light emitted from the fiber laser light source is nonpolarized light, a nonpolarization-type optical isolator is generally applied. This nonpolarization-type optical isolator emits a vertical incidence component in the laser light (forward propagation light) which arrives from the collimator in a vertical direction toward the condenser lens while emitting the vertical incidence component in the return light arriving from the condenser lens (reverse propagation light) at a predetermined exit angle toward the collimator.
The light path of the return light propagating from the optical isolator to the collimator (hereinafter referred to as ‘reverse light path’) differs from the light path of the laser light propagating from the collimator toward the optical isolator (hereinafter referred to as ‘forward light path’). Based on this fact, when an adequate distance between the collimator and optical isolator is provided, the return light from the optical isolator to the collimator is not introduced to the collimator. Thus, a conventional laser processing apparatus prevents the return light from arriving at the fiber laser light source by providing an adequate installation distance between the collimator and optical isolator (protection of fiber laser light source).